WordPress Check Post Password from anywhere

<?php

/* Check if the currently saved page password matches a specific page  */
function page_password_correct($page_id){
    if(isset( $_COOKIE['wp-postpass_' . COOKIEHASH] )){
        require_once ABSPATH . WPINC . '/class-phpass.php';
        $hasher = new PasswordHash( 8, true );
        $hash = wp_unslash( $_COOKIE[ 'wp-postpass_' . COOKIEHASH ] );
        $the_post = get_post( $page_id );
        return $hasher->CheckPassword( $the_post->post_password, $hash );

    }
    return false;
}

?>